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old SVT preamp tube question

Discussion in 'Amps and Cabs [BG]' started by THB_bassman, Feb 4, 2006.


  1. THB_bassman

    THB_bassman

    Oct 11, 2005
    socal
    The amp has been working very well, with an occasional unexplained noise, like a speaker breaking up... I am finally going through and cleaning up tube sockets, checking for bad preamp tubes...with the amp on, and plugged into a speaker, tapping on the 6C4 yields the sound through the speaker. One of the three 12DW7 tubes does the same thing. None of the poweramp tubes make noise doing the tapping. Do you think I should just get all new preamp tubes here? Or just the 2 which are noisy? I am inclined to just replace them all as long as it's open. Thanks...
     
  2. Did you clean out the socket connectors? If so, then those two tubes probably need replacing. There's no reason to replace the others.
     
  3. THB_bassman

    THB_bassman

    Oct 11, 2005
    socal
    Yes, thanks, I got some good contact cleaner / lube from RS and worked the tubes in and out and all around for a while to get them nice and clean.

    I'll order me up a 6C4 and a 12DW7 then.
    Thanks.
     
  4. THB_bassman

    THB_bassman

    Oct 11, 2005
    socal
    Just ordered the tubes from fliptops, total $17.81 including shipping. Hope this fixes the noise issue. I have searched this forum a little and found that lots of you like tubedepot.com and triode electronics. I have added those to my bookmarks along with eurotubes.com Thanks.
     
  5. ricplyrz

    ricplyrz

    Dec 26, 2005
    Just my humble opinion....why just replace what you know is bad when the other tubes are probably on their way out also. It's not that expensive to retube the preamp section and there is no debate what so ever, that a completly retubed preamp will sound better than a patched one.
     
  6. THB_bassman

    THB_bassman

    Oct 11, 2005
    socal
    I tend to agree with that; that is, as long as you're in there, replace them all. In this case the shipping is cheap, and my bank account is low, so later on I can get the rest of the tubes, hopefully before I need to, replace them all and have some spares. Thanks for your input.
     
  7. ricplyrz

    ricplyrz

    Dec 26, 2005

    You are more than welcome and I hope this solves your problem....:)
     
  8. Those tubes sound microphonic. There is absolutely NO reason to think the others have ANY need being replaced.

    You have NO idea what you're talking about in the least. Most old tubes, even well used ones, are still going to to be sonically superior to new production, especially preamp tubes.
     
  9. ricplyrz

    ricplyrz

    Dec 26, 2005

    Really? OK...well thank you for adding another reason why I belive a VR will not sound like a vintage SVT. I appreciate it.
     
  10. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The 6C4 is a particular issue..... we sure had trouble with them back making the run of 500, noise just as you say.

    We found actual NOS tubes back then.... recently made.

    I can see that being an issue, the signal level is rather low at the preamp output.

    I hope your new one is quiet. The problem is that the 6C4 is not really a typical audio tube, and may not be tested or selected for noise.
     
  11. THB_bassman

    THB_bassman

    Oct 11, 2005
    socal
    Thanks again Jerrold, I ordered a 6C4WA, if there's any difference. It should NOT be microphonic, right? And if it is, then it's no good, right?
     
  12. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    They are better, IF they really are that number.... which is the number we used.

    Did you get it from us or somewhere else? From us it should be good.

    Unfortunately ALL tubes are microphonic. The quiet ones just are not "too" microphonic.

    It's the nature of anything where the physical dimensions of "stuff" affect the performance. Tubes are clearly like that. Anything moves with vibration, you get *some* amount of noise.
     
  13. ricplyrz

    ricplyrz

    Dec 26, 2005
    Jerrold, Ampeg still sells tubes correct? Would you have any reccomendation as to a replacement for the stock sovtek power tubes in a CL? My understanding is that these tubes have a "thiner" sound as compared to other 6550's.
     
  14. THB_bassman

    THB_bassman

    Oct 11, 2005
    socal
    Jerrold, no- I wasn't aware you guys sold them, (duh...) ordered them from Fliptops.
    But I think they are a reputable company. I hope. I haven't heard any bad about them, and I had placed an order for some feet and knobs a few weeks ago, and everything seems pretty cool to me.
    The knobs are EXACT copies or else NOS, I don't know.